1. Field of the Invention
The present invention relates generally to the fields of synthetic filaments and products made therefrom. More particularly, it concerns synthetic filaments that have both low surface energy and high strength.
2. Description of Related Art
Fabrics which are water-repellent (i.e. provide a barrier to moisture) while allowing the passage of water vapor and other gases are desirable for use in apparel, shoes, tents and camping equipment, packaging, medical apparel, and medical supplies. Such fabrics require fibers that have both a low surface energy to repel water and a strength high enough to be processible into a useful fabric. Other desirable fabrics are both water-repellent and do not allow the passage of water vapor and other gases, for use in packaging and medical supplies.
In packaging, protective apparel, and industrial filtration, a need exists for fabrics that are stable to both heat and chemicals. Such fabrics require fibers both low in surface energy and high enough in strength to be processible into a useful fabric, as well as heat and chemical resistance.
One class of water-repellent fabrics are those made by applying a finish to a fabric or its component filaments before or after the weaving or knitting process. The finish is intended to provide the low surface energy needed to repel water. However, such finishes tend to have poor durability and washfastness, and often require environmentally taxing application or post-treatment steps.
A second class of water-repellent fabrics is one comprised of water-repellent materials. An example of this class is a fabric comprising polytetrafluoroethylene (PTFE) sold by W.L. Gore Inc. under the trade name GORE-TEX(copyright). Known uses of PTFE fabrics are chiefly lamination of the PTFE fabric to a textile fabric. This suggests that PTFE fabrics, although having low surface energy, do not have high enough strength to be useful fabrics per se.
Therefore, it is desirable to have a textile fabric made of filaments that exhibit low surface energy and strength high enough to be processible into useful fabrics. It is also desirable for such filaments to be produced by high throughput, economical spinning technology. Although filaments with a core/sheath structure wherein the sheath comprises a halogenated polymer are known (Chimura et al., U.S. Pat. Nos. 3,930,103 and 3,993,834), the core of the known filaments comprises primarily methyl methacrylate, and is not useful in forming textile fibers or filaments. Although core/sheath filaments wherein the core comprises nylon and the sheath comprises a grafted olefinic polymer are known, such as Tabor et al., U.S. Pat. No. 5,372,885, no such filaments are known to comprise a sheath useful in heat- and chemical-resistant textile applications.
In one embodiment, the present invention relates to a textile filament comprising a first longitudinally extending component formed of at least one filament-forming polymer, and a second longitudinally extending component formed of at least one polymer, wherein the second longitudinally extending component is in contact with the surface of the first longitudinally extending component, and wherein the filament has a contact angle greater than or equal to 90 degrees. In one embodiment, the first longitudinally extending component forms the core of the filament, and the second longitudinally extending component is in the form of a sheath that surrounds the circumference of the core. In another embodiment, the second longitudinally extending component is in the form of one or more stripes located on the surface of the first longitudinally extending component.
In another embodiment, the present invention relates to a yarn, wherein the yarns comprise a plurality of filaments as described above. The yarn may possess a contact angle greater than 90 degrees. The present invention also relates to a fabric comprising a plurality of said yarns. The spacing between the yarns may be sufficiently small to provide a barrier to liquids and sufficiently large to allow the passage of gases, or is sufficiently small to provide a barrier to liquids and to gases. The fabric may possess a contact angle greater than 90 degrees.
In a further embodiment, the present invention relates to a laminate that comprises a plurality of yarns, fabrics and/or filaments as described above. The laminate may possess a contact angle greater than or equal to 90 degrees.
Another embodiment of the present invention relates to a process for making a method for producing a low surface energy filament comprising, melting a first component comprising at least one filament-forming polymer; melting a second component comprising at least one polymer; extruding said first component and said second component to form a filament, wherein said second component is formed on said first component; quenching said filament; and drawing said filament; wherein said filament possesses a contact angle greater than or equal to 90 degrees.